Pneumatic electric switch



Jun 1951 J. NEGRO PNEUMATIC ELECTRIC swrrcn Filed Feb. 8, 1949 JNVENTOR.

John Negro BY I %M (ZOHSCQUGIICGS.

Patented June 12, 1951 PNEUMATIC ELECTRIC SWITCH John Negro, Chicago,Ill., assignor of one-third to Sydney R. Kramer and one-third to EdwardA. Faley, both of Chicago, 111.

Application February 8, 1949, Serial No. 75,269

8 Claims.

large number of signal lights which are general- .ly controlled bypneumatic switches located on the trailer and operated by pneumaticpressure controlled from the cab or drivers position. Such switches arefrequently subjected to abuse or misuse by the operator and musttherefore be exceedingly sturdy or'rugged to withstand not only therigorous treatment to which it is normally subjected but also theoverloading to which it may be subjected by careless operators. Suchswitches must be certain in their operation since the failure of theswitch may result in serious It is one of the objects of the presentinvention to provide a switch of the above mentioned character which isso constructed that the heat produced by the flow of current andproduced by the arcing during current interruption .cannot affect theactuating parts of the switch.

The switch of the present invention comprises a body and a cap forming acasing. the body having acylinder therein in which an actuating" pistonmoves, the arrangement being such that the casing always has atmosphericpressure on one side of the piston and is arranged to receive thepneumatic pressure on the other side of the piston for moving it in onedirection. A spring is provided for returning the piston upon release of,the pneumatic pressure. It is an object of the present invention toprovide an arrangement wherein the spring as well as the piston pressuresealing means are entirely outside of the current carrying portions ofthe switch and are also insulated from the heat of an arc that may beformed during circuit interruption. As a result the, Spring retains itsresiliency over long periods tr time and also there is no danger ofcarbonization of the leather packing cup of the piston. It is a furtherobject of the present invention to provide a structure of the abovementioned character wherein the number of parts is reduced to a minimumand wherein the amount of required accurate machining is also kept to aminimum.

It is a still further object of the present invention to provide aswitch of the above mentioned character which is so arranged that it maybe mounted in position by the same switch part that extends thepneumatic pressure connection to the switch.

., The attainment of the above and further ob- 2 jects of the presentinvention will be apparent from the following specification taken inconjunction with the accompanying drawing form ing a part thereof.

In the drawing:

Figure l is a top view of the switch;

Figure 2 is a longitudinal sectional view taken along the line 22 ofFigure l;

Figure 3 is a bottom view of the switch; and

Figure 4 is a sectional view taken along the line 44 of Figure 2 andlooking in the direction of the arrows.

Reference may now be had more particularly to the drawing wherein likereference numerals designate like parts throughout.

The switch of the present invention, which is indicated in general bythe reference numeral I, is adapted to be used, as heretofore stated,for controlling the turning on and ofi of signal lights on anautomobile, an automobile truck or trailer, or on automobile trucktrailers. The switch I comprises a body 2 and a cap 3 which togetherform a casing. The body 2 has at its lower end a hollow neck 4 thatis'extern'ally threaded'so that the neck may be threaded into a pipe orfitting of the controlled pressure line of the automobile truck, thatneck serving to support the switch and also extend pressure to theswitch. To that efiect the neck 4 has a bore 6 extending longitudinallythereof. Above the neck the body 2 has an intermediate body portion 8that has an outwardly extending enlargement or flange 9 for receivingthe cap 3. The intermediate body portion has a cylindrical bore I0formed therein with its longitudinal axis in alignment with the axis ofthe bore 6 in the neck 4. At the bottom of the cylinder bore lo theintermediate body portion 8 has an inwardly projecting ledge II thatserves as a guide for a piston stem, to be more fully described as thisspecification proceeds. The ledge H has a series of small holes l2formed therein to maintain communication between the interior of theneck 4 and the cylinder bore III.

A piston is mounted within the cylinder bore 7 I e. The piston comprisesa leather pressure cup I5 that slides in the cylinder bore in and makesa sealing sliding fit around the entire periphery of the bore In. Thepressure cup I5 is secured to a spacer 16, preferably of heat insulatingmaterial such as, for instance, fiber.. The material of the spacer I6 isalso an electric insulator. The spacer i6 is of a cylindrical shape andhas centrally located aligned threaded bores l'|l1' at opposite endsthereof. The cup It fits against the bottom of the spacer l6 and issecured in place by means of a circular metal washer l8 and a pistonstem 19. The piston stem is made of steel and has a threaded stud 22integral therewith which stud passes through the pressure cup l andthreads into the bore H in the spacer IS. The piston stem also has as anintegral part thereof an enlarged cylindrical portion 25 that bearsagainst the washer l2 and presses it firmly against the pressure cupand. presses the pressure cup against the spacer It. The bottom of thecylindrical portion 25 of the stem serves as a stop to limit thedownward movement of the piston. The piston stem I? has at the bottomthereof a cylindrical rod 21 that slides through the ledge H and isguided thereby. At its lower end the rod 21 has a screw 28 threadedtherein, that screw having a head which forms a seat for a return spring29 that surrounds the rod 27. The opposite end of the spring 29 bearsagainst the bottom of the ledge II. The spring thus constantly forcesthe piston stem, and therefore the piston, to the switch open positionillustrated in Figure 2. At its upper end the spacer [6 has a coppercontact bridging member 32 secured thereto as by means of a screw 33threaded into the bore ll".

The cap 3 is preferably made of a suitable electrical insulatingmaterial such as, for instance, fiber. Two similar contact screws 36-36are mounted in the cap. Each screw includes a head 31 and a threadedshank 38, the shank extending through the cap 3 and being locked inplace by a lock nut 39. The shank 38 extends beyond the lock nut forreceiving the electrical connections. The heads 3'! of the two sonnetscrews are adapted to be engaged by the bridging member 32 when thepiston is moved to its elevated position. To permit such movement of thepiston the cap is hollowed out on its under side and also has a cavityinto which the head of the screw 32 may extend. There is thus formed'alow pressure chamber 42 where the contacts are located, that chamberbeing open to atmosphere by a venting opening 43. The cap is secured inplace on the body 2 by a number of screws 45, five such screws beingill'us trated.

Itis believedthat the operation of the switch will be obvious from thedescription given above.

When air pressure is applied to the interior of the neck 4 that pressureextends through the holes l2 into the pressure chamber at the bottom ofthe piston and forces the piston upwardly against the action of thereturn spring 1 9. The bridging member 32 makes contact with the heads'31 at the bottom of the two contact screws 36 and thus establishes acircuit between them. To open the switch it is merely necessary torelease the air pressure applied to the switch through the neck 4. Thespring 29 then moves the piston to its switch open position. The heatproduced at the contacts by the current flowing therethrough or by theare that forms during circuit interruption is at a considerable distancefrom the spring 25 and therefore there is little danger of overheatingthe spring, which would impair its resiliency. It is also at aconsiderable distance from the leather pressure cup l5 and separatedfrom the pressure cup by the insulating spacer It so that the leathercup is not likely to be adversely affected by heat produced by theswitch. In the event of pitting of the contacts they may be easilyremoved and replaced, and the bridging member 32 can also easily bereplaced. Furthermore, the bridging member is in the form of a plaincopper washer so that if any pitting occurs on the washer at the placeswhere the washer makes contact with the contacts 3'! it may not even benecessary to replace the washer because the washer can be turned througha small arc and thus change the location of the points of engagementbetween the washer and the contact heads 31.

In compliance with the requirements oi the patent statutes I have hereshown and described a preferred embodiment of my invention. It is,however, to be understood that the invention is not limited to theprecise construction here shown, the same being merely illustrative ofthe principles of the invention. What I consider new and desire tosecure by Letters Patent is:

l. A pneumatic pressure operated switch ineluding a casing comprising abody and a cap, the body having a hollow straight neck at one end openfor receiving pneumatic pressure, the neck merging into an intermediatebody portion, a piston-receiving cylinder in said intermediate bodyportion, a piston in said cylinder and dividing the easing into a highpressure chamber at the stem end thereof and a low pressure chamber atthe cover end thereof, said piston comprising a flexible pressuresealing member s1idable in the cylinder and making a sealing fit withthe wall thereof, the sealing member being on the pressure chamber sideof the piston, the piston including also a heat insulating cylindricalspacer slidable in the cylinder and secured to the sealing member andseparating it from the low pressure chamber, a. piston stem extendinglengthwise into the neck, spring means on the pressure side of thepiston for moving the piston in a direction opposite to the direction inwhich it is moved by pressure in the high pressure chamber, switchcontacts on the inside of the low pressure chamber, and a contactbridging member mounted on the side of the spacer remote from theflexible sealing member and actuated by the spacer to close and open acircuit between the contacts in the low pressure charm her, the spacerserving to insulate the sealing means and the spring from heat producedby arcing at the switch contacts in the low pressure chamber, andventing means opening the low pressure chamber to the atmosphere.

2. A pneumatic pressure operated switch including a casing comprising abody and a cap, the body having a hollow straight neck at one end openfor receiving pneumatic pressure, the neck merging into an intermediatebody por-- tion, a pisto'n recei'vi'ng cylinder in said inter mediatebody portion, an outwardly extending cover-receiving flange surroundingthe intermediate portion at the end thereof remote from the neck, meanssecuring the cover to said flange, a piston in said cylinder anddividing the easing into a high pressure chamber at the stem end thereofand a low pressure chamber at cover end thereof, said piston comprisinga -lexible pressure sealing member slidable in the cylinder and making asealing fit with the wall thereof, the sealing member being on thepressure cham her side of the piston, the piston including also a heatinsulating cylindrical spacer slidable in the cylinder and secured tothe sealing member and separating it from the low pressure chamber, apiston stern secured to the piston and securing the sealing member tothe cylindrical spacer, said stem extending lengthwise into the neck,spring means on the pressure side of the piston for moving the piston ina direction opposite to the direction in which it is moved by pressurein the high pressure chamber, said spring being located in the hollowneck and surrounding the stem, switchcontacts on the inside of the lowpressure chamber, and a contact bridging member mounted on the side ofthe spacer remote from the flexible sealing member and actuated by thespacer to close and open a circuit between the contacts in the lowpressure chamber, the spacer serving to insulate the sealing means andthe spring from heating produced by arcing at the switch contacts in thelow pressure chamber, and venting means opening the low pressurechaiuberto the atmos phere. v .3. A pressure operated switch including a casingcomprising a body and a cap, the body having a hollow straight neck atone end threaded for mounting the body and hollow and open for receivingpneumatic pressure at its mounted end, the neck merging into anintermediate body portion of increased diameter and in line therewith, apiston-receiving cylinder in said intermediate body portion, a piston insaid cylinder and dividing the casing into a high pressure chamber atthe stem end thereof and a low pressure chamber at the cover-endthereof, said pis ton comprising a flexible pressure sealing memberslidable in the cylinder and making a sealing fitwith the wall thereof,the sealingrnernber being on the pressure chamber side of the piston,the piston including also a heat insulating cylindrical spacer slidablein the cylinder and secured to the sealing member and separating it fromthe low pressure chamber, a piston stem secured to the piston andsecuring the sealing member to the cylindrical spacer, said stemextending lengthwise into the mounting neck, spring means for moving thepiston in a direc tion opposite to the direction in which it is moved bypressure in the high pressure chamber, said spring being located in thehollow neck and sur rounding the stem, means at one end of the stemconstituting a stop for the spring, switch contacts carried by the coveron the inside of the low pressure chamber, and a contact bridging membermounted on the side of the spacer remote from the flexible sealingmember and actuated by the spacer to close and open a circuit betweenthe contacts in the low pressure chamber, the spacer serving to insulatethe sealing means and the spring from heat produced by arcing at theswitch contacts in the low pressure chamber, and venting means openingthe low pressure chamber to the atmosphere.

4AA pressure operated switch including a casing comprising a body and acap, the body having a hollow straight neck at one end threaded formounting the body and hollow and open for receiving pneumatic pressureat its mounted end, the neck merging into an intermediate body portionof increased diameter and in line therewith, a piston-receiving cylinderin said intermediate body portion, an outwardly extendingcover-receiving flange surrounding the intermediate portion at the endthereof remote from the neck, means securing the cover to said flange, apiston in said cylinder and dividing the casing into a high pressurechamber at the stem end thereof and a low pressure chamber at the coverend thereof, said piston comprising a flexible pressure sealing memberslidable in the cylinder and making a sealing fit with the wall thereof,the

sealing member being on the pressure chamber side of the piston, thepiston including also a heat insulating cylindrical spacer slidable inthe cylinder and secured to the sealing member and separating it fromthe low pressure chamber, a piston stem secured to the piston andsecuring the sealing member to the cylindrical spacer, said stemextending lengthwise intothe mounting neck, spring means for moving thepiston in a direction opposite to the direction in-which it is moved bypressure in the high pressure chamber, said spring being located in thehollow neck and surroundin the stem, means at one end of the stemconstituting a stop for the spring, switch contacts carried by the coveron the inside of the low pressure chamber, and a contact bridging membermounted on the side of the spacer remote from the flexible sealingmember and actuated by the spacer to close and open a circuit betweenthe contacts in the low pressure chamber, the spacer serving to insulatethe sealing means and the spring from heat produced by arcing at theswitch contacts in the low pressure chamber, and venting means openingthe low pressure chamber to the atmosphere.

5. In a pressure operated switch,a casing comprising a body and a cap,the body having a high pressure chamber and a low pressure chamber and acylinder bore connecting said chambers, a piston in said cylinderclosing off com munication between the chambers,- said body having amounting neck in alignmentwith the longitudinal axis of the cylinder andwhich neck is part of the high pressure chamber, switch contacts in saidlow pressure chamber, said low pressure chamber being open to theatmosphere, the piston including on the high pressure side thereof aflexible pressure sealing member slidable in and making a sealing fitwith the cylinder wall and a heat insulating cylindrical spacer to oneside of which the pressure sealing 'inember is secured, the spacerextending to the low pressure chamber, a contact bridging member securedto the spacer on the side thereof in the low pressure chamber, a pistonstem secured to the piston and securing the flexible sealing member tothe spacer, said stem extending in the mounting neck, a springsurrounding the stem in the mounting neck and urging the piston stem inone direction, the piston being moved in the opposite direction bypressure in the high pressure chamber.

6. In a pressure operated switch, a casing comprising a body and a cap,the body having a high pressure chamber and a low pressure chamber and acylinder bore connecting said chambers, a piston in said cylinderclosing off communi cation between the chambers, said body having amounting neck in alignment with the longitudinal axis of the cylinder,said body having a perforated projection on the inside thereof betweenthe part of the body constituting the neck and the part forming thecylinder, switch contacts in said low pressure chamber, said lowpressure chamber being open to the atmosphere, the piston including onthe high pressure side thereof a flexible pressure sealing memberslidable in and making a sealing flt with the cylinder wall and a heatinsulating cylindrical spacer to one side of which the pressure sealingmember is secured, the spacer extending into the low pressure chamber, acontact bridging member secured to the spacer on the side thereof in thelow pressure chamber, a piston stem secured to the piston, said stemextending passages pressure chamber.

7. Infapressure'ioperated switch, a casing-comprisingiasbody :and :acap, the body having a high pressure chamber and a low pressure chamber:and a cylinder bore connecting .said chambers, 'ra piston in saidcylinder closing off communication .between the Lchambers, .said bodyhaving a mounting :neok opening into the high pressure chamber, switchcontacts in said low pressure chamber. said low .';p1'essure chamber:being open to the atmosphere, the piston including on the high pressureside "thereof ,a flexible pressure sealing imember slidable in andmaking a sealing fit with the cylinder wall and a :heatinsulating'cylindr-ical spacer to one side of which ?the pressuresealing member is secured, the spacer extending to the low pressurechamber, a contact bridging member secured to the spaceron the low"pressure side thereof, and spring means in the high pressure chamberurging the piston in one direction, the piston being moved in theopposite direction .by pressure in the high pressure chamber.

,8. In :apressure operated switch,aa casing 'comprisinga body-and :acap, the bodyhaving a high pressure :chamber and a low pressure chamberand a cylinder bore connecting said chambers, a piston in said cylinderclosing off communication'between the chambers, said body having amounting :neok opening into the high pressure chamber, switch contactsin said low pressure chamber, said low pressure chamber being open tothe atmosphere, the piston including on'the high pressure side thereof aflexible pressure sealing member slidable in and making a sealing fitwith the cylinder wall and a heat insulating cylindrical spacer to oneside of which the'pressure sealing member is secured, the spacerextending to the low pressure chamber, a contact bridgingmember securedto the spacer on "the low pressure side thereof, piston stop means onthe inside of the-body on the'high pressure side thereof for limitingthe movement of the piston in one direction, said piston having a stemextending therefrom past the stop means, and a piston return springbearing at one end on the stem and at the other end against the stopmeans on the side thereof remote from the piston, and spring means inthe 'high pressure chamber urging the piston in one direction, thepiston being moved in the opposite direction by pressure in the highpressure chamber.

JOHN NEGRO.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,909,699 Mahan May '16, 19331,951,882 Penetcost Mar. 20, 1934 2,292,378 Jensen Aug. 11, 1942

